415
Cellular Composition of Water Buffalo Mammary Gland and its Proliferation Status During Dry and Mastitis
Mammary alveoli, composed of mammary epithelial cells, are the structural and functional unit of mammary gland; secrete milk into the alveolar lumen. Milk production is directly related to secretory activity and number of alveolar cells. Alternation in cellular composition, in particular alveolar cells, thus has a direct role in volume of milk secretion. We collected mammary tissues of milking water buffalo from slaughterhouse for the purpose of evaluation of its cellular composition, proliferation status and identification of myoepithelial cells. Out of twenty-one buffaloes, ~80% of mammary samples were from the dry animals (evidenced by presence of small non-secretory epithelial cells and virgin-like state of the gland) and ~ 20% of samples were from the lactating animals. All the lactating animals were affected with mastitis (suggested by the presence of fibrin clots, cellular debris and loss of alveolar epithelium), which were also confirmed by a veterinary pathologist. The fraction of total mammary epithelium (large secretory and small non-secretory cells; mean % +/- S.E) did not differ in dry vs. lactation period (22.6 +/- 1.66 vs. 18.7 +/- 3.59; P >0.05). However, number of small non-secretory epithelium were greater in dry period (22.6 +/- 1.66 vs. 10.1 +/- 2.97; P = 0.006) than the lactation period, likely due to differentiation of non-secretory cells into secretory cells. Number of myoepithelial cells (identified by vimentin expression in basal layer of epithelium) were greater (23.38 +/- 2.89 vs. 5.55 +/- 1.10; P = 0.004) in mastitis than the dry animals. Increased expression of vimentin (also a marker of migrating cells) in the stroma, suggested the role of cell migration in inflammation, tissue regeneration and immune response during mastitis. Thus, mastitis animals had increased number of myoepithelial cells and stromal migratory cells in their mammary glands. A greater number of myoepithelial cells during mastitis was concomitant with increased (5X) expression of Ki-67, a marker of cell proliferation. This study demonstrates cellular composition of buffalo mammary glands as well as supports the idea that infection of mammary gland enhances proliferation of mammary epithelial cells.
Keywords: Water buffalo mammary gland, cellular composition, vimentin, proliferation